I. Field of the Invention
The present invention relates to spray coating booths for trapping and collecting air-borne coating overspray which has been discharged from a coating spray gun or other application device and more particularly to spray coating booths having a movable wall of filter material.
II. Description of the Prior Art
There are three types of spray booths available and used throughout this industry.
Type No. 1: The most universally used type is the water-wash spray booth. The water-wash type spray booth is generally considered to be the most efficient spray booth available but the efficiency ratings are directly related to the operating conditions, maintenance and a variety of other factors. A properly operated, clean, water-wash spray booth is rated anywhere from 80% to 92% efficient in collecting and trapping, with water, air-borne paint particles. The collection is accomplished using a variety of "water curtains" and "eliminator" (baffle) plates over which the paint particles are drawn by use of an exhaust fan. The paint particles collected are trapped in a water pan (tank), chemically treated to form a sludge, and then periodically removed for disposal.
The major disadvantages of water-wash paint spray booths are:
1. Approximately 8 to 20 percent of the air-borne paint over-spray is exhausted from the booth to the atmosphere. PA0 2. Restrictions in disposing of collected overspray (sludge). PA0 3. High cost of proper booth maintenance. PA0 4. Restrictions in obtaining desired uniform air flow required for ideal spraying conditions. PA0 5. Large quantities of water are recirculated (approximately 30 GPM per lineal foot of booth). PA0 7. Fire hazard due to presence of paint residue on both `eliminator` plates, plenum walls, fan blades and exhaust stack. PA0 1. Low efficiency in collecting air-borne paint particles. PA0 2. High cost in replacing filters. (usually daily). PA0 3. Restrictions in disposing of paint-soaked filter pads. PA0 4. Large quantity of exhaust air required. PA0 5. High level of fire hazard. PA0 6. Large volume of exhausted air-borne paint particles depositing on property surrounding paint operation. PA0 1. Limitations in width and height of booth sections. PA0 2. Inconsistent quality of filter material (tears). PA0 3. 10% to 20% filter waste. PA0 4. Relative high labor cost to load and unload filter media.
6. Large volume of air necessary to perform collection action required.
Type No. 2: The dry filter type paint spray booth is commonly used throughout industry for touch-up spraying, batch operations and in increasing number, as production spray booths. The filter type booth employs a paint arrestor pad (filter) which is constructed of fiberglass or other materials, (similar to a furnace filter). Filters are normally 20".times.20".times.1" in size and are arranged to form the front wall of an exhaust plenum which includes an exhaust fan designed to draw air-borne paint particles into the filter media. Generally filter booths of this type are rated 70% efficient, in that at least 30% of the air-borne paint particles are drawn through the filter pads and are discharged out the exhaust fan and stack to the atmosphere.
The main disadvantages of the dry filter type paint spray booth are:
Type No. 3: The third type of booth is generally referred to as a "roll-filter" spray booth. The roll filter booth is very limited (less than 1%) in use in this industry. The only roll-type filter booth available is referred to in U.S. Pat. Nos. 2,875,680; 2,841,073; 3,071,060; and 3,811,371. This roll-filter paint spray booth is designed using a 60" wide, 400 ft. long roll of non-woven cotton shoddy fabric which is positioned on top of the booth enclosure, drawn downward to form the front wall (single curtain) of an exhaust plenum. The exhaust plenum is equipped with an exhaust fan which is designed to draw the air-borne paint overspray into the `filter curtain` thus entrapping particles. As the filter curtain becomes saturated with paint articles the curtain indexes by use of a drive on the wind-up shaft, exposing fresh filter.
Under certain conditions this booth can be 100% efficient in collecting and trapping air-borne paint particles. However, design limitations and inconsistent quality of filter material normally allows a much lower efficiency factor in its ability to consistently trap air-borne paint particles.
The major disadvantages of the roll-type filter paint spray booth are:
Based on our investigations we concluded that there is a definite need by the finishing industry for a paint spray booth designed, not only to fulfill the industry needs but also to accommodate current and anticipated E.P.A., OSHA, and Insurance requirements.